Plot
At Kuranose High School in Tokyo, Japan, 17-year-old Makoto Konno discovers a message written on a blackboard that reads "Time waits for no one" and ends up inadvertently falling onto a walnut-shaped object. On her way to the Tokyo National Museum to meet with her aunt, Kazuko Yoshiyama, she is ejected into a railroad crossing when the brakes on her bicycle fail and hit by an oncoming train, but finds herself transported back in time when she was riding her bicycle right before the accident. After telling Kazuko what happened, she helps Makoto realise she now has the power to "time-leap", the ability to literally travel through time. At first, Makoto uses her powers to avoid being late, achieve perfect grades, avoid mishaps and even relive a single karaoke session for several hours, but soon discovers her actions can adversely affect others.
Consequently, Makoto uses most of her leaps frivolously to prevent undesirable situations from happening, including an awkward love confession from her best friend, Chiaki Mamiya. Makoto realises she has a numbered tattoo on her arm indicating the limited number of times she can time-leap. Using her remaining time-leaps, Makoto attempts to make things right for everyone. When Chiaki calls Makoto to ask if she has been time-leaping, she uses her final time-leap to prevent Chiaki's call. In the meantime, Makoto's friend Kōsuke Tsuda and his new girlfriend, Kaho Fujitani, borrow her faulty bike. Makoto attempts to stop them, but as she had just used her final leap, she is unable to rescue them from being hit by the train.
A moment later, Chiaki freezes time. Telling Makoto he is from the future, he explains the walnut-shaped object is his time-traveling device, and used it to time-leap hoping to see a painting that Kazuko is restoring, as it has been destroyed in the future. While walking with Makoto in the frozen city, Chiaki explains why he stayed longer in her time than he originally planned. Consequently, he has used his final leap to prevent Kōsuke and Kaho from the train accident and he has stopped time only to explain to Makoto he is unable to return to his own time period, and having broken the rules by revealing his origins and the nature of the item that allowed Makoto to leap through time, Chiaki must leave. Makoto then realises she is in love with him.
True to his words, Chiaki disappears once time resumes. Initially distraught by Chiaki's disappearance, Makoto discovers Chiaki's time-leap inadvertently restored her final time-leap: Chiaki leaped back to the time before Makoto used it. Makoto uses it to safely leap back to the moment right after she originally gained her powers; Chiaki would still have his one remaining time-leap. Recovering the used-up time-travel device, she explains her knowledge of everything as she shows it to Chiaki. Makoto vows to ensure the painting's existence so Chiaki can see it in his era. Before Chiaki departs, he tells Makoto he will be waiting for her in the future. When Kōsuke asks her where Chiaki went, she tells him Chiaki went to study abroad. She has made a decision about her own future.
